CVE-2024-4771Public exploitNetwork attack vector

Browser crash via stale HarfBuzz blob pointer

Published May 14, 2024 · Updated Aug 1, 2024

Use-after-free in Firefox before 126 allows remote attackers to crash the browser through crafted web content after an allocation failure. In gfx/thebes/gfxFontEntry.cpp, hb_object_create frees user_data on failure while mSharedBlobData retains the freed pointer for later reuse by ForgetHashEntry. The trigger requires failure of a 48-byte allocation near memory exhaustion; a crash was reproduced, but public evidence does not demonstrate code execution.

CVSS severity8.6
High
EPSS probability0.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Firefox before 126 allows remote attackers to crash the browser through crafted web content after an allocation failure. In gfx/thebes/gfxFontEntry.cpp, hb_object_create frees user_data on failure while mSharedBlobData retains the freed pointer for later reuse by ForgetHashEntry. The trigger requires failure of a 48-byte allocation near memory exhaustion; a crash was reproduced, but public evidence does not demonstrate code execution.

The record

CVE
CVE-2024-4771
Published
May 14, 2024
Updated
Aug 1, 2024
Vendor
Mozilla
Product
Firefox
Classifications
CWE-416, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 14, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 1, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <126
  2. Affected versionversion=unspecified <126

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=0 <126; version=unspecified <126

Published CVSS scores

8.6NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-416Use After Free
T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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